From the Guidelines
Absorption is the pharmacokinetic parameter least affected by the aging process. While aging significantly impacts other pharmacokinetic parameters such as metabolism and elimination, absorption remains relatively stable in elderly patients compared to younger adults. According to 1, age-related changes in absorption include decreased gastric acid production and emptying, which can delay absorption, but the amount absorbed remains unchanged. Additionally, decreased splanchnic blood flow, motility, and absorption surface can be affected by antacids and laxatives, but the overall effect on absorption is minimal. In contrast, other pharmacokinetic parameters show more consistent age-related changes, with hepatic metabolism often decreasing due to reduced liver mass and blood flow, and renal elimination declining due to decreased glomerular filtration rate. Understanding this relative stability of absorption is important when adjusting medication regimens for elderly patients, as it helps clinicians focus more on adjusting for changes in drug clearance rather than absorption.
Some key points to consider:
- Age-related changes in absorption are relatively minor compared to changes in metabolism and elimination 1
- Decreased gastric acid production and emptying can delay absorption, but the amount absorbed remains unchanged 1
- Hepatic metabolism and renal elimination are more significantly affected by aging, with decreased liver mass and blood flow, and decreased glomerular filtration rate, respectively 1
- Clinicians should focus on adjusting for changes in drug clearance rather than absorption when prescribing medications for elderly patients 1
From the Research
Pharmacokinetic Parameters Affected by Aging
The aging process affects various pharmacokinetic parameters, including:
- Absorption: Age-related decreases in gastric acid secretion, gastrointestinal motility, and blood flow may alter drug absorption, but no significant age-related change in drug absorption is observed 2.
- Distribution: With aging, body fat increases and total body water decreases, affecting the volume of distribution of hydrophilic and lipophilic drugs 3, 2.
- Metabolism: Age-related reduction in liver size, hepatic blood flow, and hepatic drug-metabolizing enzyme activity decreases the hepatic drug clearance 2.
- Excretion: The decreases in renal blood flow, glomerular filtration rate (GFR), and tubular secretion have a considerable impact on the renal clearance of drugs 2.
Least Affected Parameter
Based on the available evidence, absorption is the pharmacokinetic parameter that is least affected by the aging process, as no significant age-related change in drug absorption is observed 2.
Comparison of Options
Comparing the options: